Pt-M Thin Film Catalyst Synthesis for Olefin Epoxidation Using Water As O Atom Source

Production of propylene oxide with hydrogen peroxide requires the direct burning of fossil fuels to reach elevated reaction temperatures. Electricity can serve as a greener alternative to fossil fuels, sustainably functionalizing olefins with the aid of efficient and selective electrocatalysts. However, understanding mechanisms of electrochemical reactions remains untrivial due to dynamic changes of the catalysts under applied potential. Olefin epoxidation using water as the oxygen atom source has been previously demonstrated in ambient conditions with PtM bimetallic nanoparticles as the catalyst drop-cast onto carbon paper (CP) electrodes (M. Chung, PhD Thesis, MIT), achieving a Faradaic efficiency (FE) higher than 90% for cyclooctene oxide. Due to its porous nature, CP is regarded as an unsuitable substrate for in situ spectroscopies that require an ultra-high vacuum environment, such as soft X-ray absorption spectroscopy. By changing the substrate to a nonporous material and depositing the catalyst without sacrificing its high catalytic performance, the mechanism of this oxidation reaction can be investigated to reveal the reason why PtM excels as a novel catalyst for olefin epoxidation. This study provides insight on how deposition methods of PtM affect its structure and catalytic properties by analyzing the FE obtained from the use of CP, indium tin oxide, and glassy carbon as substrates. PtM thin films were prepared by drop-casting, sputtering, and spin coating, and chronopotentiometry was carried out at 40 mA/cm² until a total charge of 20C was passed. Scanning electrode microscopy characterization was performed to obtain information on the surface morphology of sputtered PtM thin films.